USA, California: Exploring Long Valley's Geothermal System

Mapping Water and Heat Deep Under Long Valley Caldera (EOS)

Researchers use electrical resistivity to find the heat source and reservoir feeding Long Valley Caldera's labyrinthine hydrothermal system.

View of part of the Long Valley Caldera with Mono Lake in the background, taken from the summit of mammoth Mountain. Taken by Ian Crawford, GRC Fieldtrip September 2015.

Long Valley Caldera is a volcanic depression near Mammoth Mountain in California, which has experienced extensive hydrothermal activity over two periods of time since it formed about 767,000 years ago. The caldera is home to an active hydrothermal system, which has been extensively studied close to the surface but less well characterized deeper underground. Hot fluids flow underground and escape to the surface through hot springs, but the heat source and reservoir for the labyrinthine hydrothermal system have not been thoroughly studied.

Now, Peacock et al. have used magnetotellurics to create a three-dimensional (3-D) model of the ground down to 10 kilometers underneath the Long Valley volcanic system. To create this 3-D model, the team measured the Earth’s electrical response to natural magnetic fields at 61 stations across Long Valley Caldera.

(Thanks to GRC Member Marcelo Lippmann, Staff Scientist (retired) at Lawrence Berkeley National Laboratory for the submission.)

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